When Ih was blocked with 20 mM CsCl, the oscillatory trajectory of the MG and GM neurons became pyloric like. A1, A2, C1, and C2: 1, depolarizing phase; 2, plateau phase; 3, repolarizing phase; 4, valley. A2, B2, C2, and D2: after application of 20 mM CsCl, the oscillatory trajectory of the MG and GM neurons changed toward sinusoidal like, and the pyloric modulation was diminished. A1, B1, C1, and D1: gray traces show the orignal voltage traces, and black traces show the slow oscillations after filtering.